Benefits and disadvantages of dams

Lesson 3: Water resources

Benefits and disadvantages of dams


Rainwater is conserved through walls and reservoirs, bunding of streams and canal systems. Constructing large dams and reservoirs have benefits and drawbacks.


  • Water from rain and melting snow can be captured and stored.
  • This stored can be released to produce hydro electric power; irrigate land below the dam; control flooding land below the reservoir; provide water carried to towns and cities by aqueducts.
  • Reservoirs are used for recreation activities such as swimming, fishing and boating.
Disadvantages/ environmental impacts:

The impacts could be classified into three categories.

  1. Impacts within and around the area covered by the dam and reservoir

  2. Downstream effects caused by alteration in hydraulic regime

  3. Regional effects in terms of overall aspects including resource use and socio-economic aspects.

  4. The impacts caused by construction of dams and reservoirs include changes in the microclimate, loss of vegetable cover, soil erosion, variation in water table and enhanced seismic activities due to pressure of water. In hilly tracts, blasting operations, for road construction can cause considerable damage to the environment through loosening of hillsides and resultant landslides, sedimentation of reservoirs, drying up of spring and flash floods. Creation of new settlements for the workmen and rehabilitation of project oustees in the watershed areas are becoming major problem.
    In many places, dams almost eliminate sediment from rivers downstream, causing serious problems in the plains where farmers need sediments to fertilize their fields. As a result of the clearing of vast forest land upstream, huge quantities of soil are washed into the river dams. All these factors contribute to siltation rates.

Last modified: Wednesday, 28 December 2011, 7:53 AM